Evolution of the beam divergence and other output characteristics of lamp-pumped dye lasers

The beam divergence and other output characteristics of dye lasers pumped by coaxial flashlamps have been studied experimentally. The divergence of the output beam is governed primarily by the simultaneous existence of, and competition between, refractive ray paths and closed paths. The refractive paths result from thermal distortions of the active medium. The closed paths exist in the cavity because of Fresnel reflection at the cell walls. The experiment results agree satisfactorily with the conclusions of a previous analysis. Some practical recommendations are offered for developing efficient dye lasers with a highly directional output.